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OWA looks different and is unresponsive

Moshiur (Moshiur Khan) 80 Reputation points
2026-05-17T04:34:53.4066667+00:00

Hey Community.

Ever since the CVE released on May 14th, some of our users are opening outlook view to this:
User's image

The left pane is mostly unresponsive and honestly having more than 5 users have this issue is appalling alone.

Anyways, If you guys have any clue, please feel free to share.
Exchange environment is 2016 CU23. Planning to move to SE but for now, help with this.

Thanks :D (ignore the Exchange online tag, the ai generated that one)

[Moderator's note: Moved from Exchange Online]

Exchange | Exchange Server | Management
Exchange | Exchange Server | Management

The administration and maintenance of Microsoft Exchange Server to ensure secure, reliable, and efficient email and collaboration services across an organization.

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  1. Jayden-P 22,140 Reputation points Microsoft External Staff Moderator
    2026-05-17T06:58:29.9533333+00:00

    Please note that we're not Microsoft support, this is a user-to-user support forum. Moderators have no backend access and cannot directly intervene in Microsoft products. We provide only technical guidance and best-practice recommendations based on reported issues

    Hi Moshiur (Moshiur Khan)

    From this article, Addressing Exchange Server May 2026 vulnerability CVE-2026-42897 | Microsoft Community Hub, Microsoft disclosed CVE-2026-42897, a reported vulnerability affecting Exchange Outlook Web Access (OWA).

    So OWA might have some unexpected behavior, especially when mitigation is applied. May I ask did you apply the mitigation?

    If yes, there are a few known issues when mitigation is applied:

    User's image

    As for now, Microsoft is working on and will release and announce a security update for impacted versions of Exchange Server in the future. Update will be released for Exchange SE RTM, Exchange 2016 CU23, Exchange Server 2019 CU14 and CU15 (if you are running older CU versions, please update now).

    Exchange 2016 and 2019 updates will be released only to customers who are enrolled in the Period 2 Exchange Server ESU program as per Announcing Period 2 Exchange 2016/2019 Extended Security Update (ESU) program. Period 1 only ESU customers will not receive this update as that ESU program ended in April 2026.

    I hope this information helps.

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

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